Safety overload device



H. E. M CABE SAFETY OVERLOAD DEVICE Jan 311, 1928.

Filed Dec 21. 192 5 3 Shams-Sheet l INVENTOR. 1125.1. M" CABE X2 ATTORNEYS.

Jan. 31, 1928. 1565?,681

. I. E. McCABE SAFETY OVERLOAD DEVI CE Filed Dec. 21, 1 925 3Sheets-Shea 3 INVENTOR. .IRA. E. M CABE,

afiu zm M A TTORNEYS.

Jan. 31, 1928, 1,657,681

I. E. M cABE SAFETY OVERLOAD DEVICE Filed Dec. 21, 1925 5 Sheets-Sheet 5INVENTOR. 1RA.E. M CASE.

BY M

A TTORNEYS.

Patented Jan. 31, 192 v 1,657,681

TENT OFFICE.

IRA E. menu, or CHICAGO, ILLnvoIs. v 4 sen-nar OVERLOAD Jmvrcn.

UNITED STATES, PA

Application filed December 21, 1925. Serial No. 78,791.

This invention relates to improvements in. Figures 6 and 7 are viewssimilar to Figoverload safety devices and more partlcuures and 6 of amodification 1n which Figlarly to a deviceof this'character when emure 7illustrates the position assumed by ployed in connection with a switchfor conthe parts when the device has been operated 55 5 trolling anelectric circuit actuated by an by the normal expansion of the Bourdonexpansible and contractable member. tube and overload of current. v

It is an object of this invention to pro- The embodiment of thisinvention as vide a safety device for electric switches illustrated,includes a casing 1 in which is which will operate to' prevent burningout mounted a Bourdon tube 2 the open end 3 60 of the switch or theburning out of a motor of which is adapted to be connected to an whenplaced in circuit with the switch. instrumentality either directly orthrough It is also an object of this invention to a thermal bulb, whichwill cause the tu e include in such safety device a heat gento beafi'ected by variations in pressure or crating element adapted torelease the temperature of said instrumentality. The 06 switch and openthe circuit when the amfree end of the Bourdon tube is connected perageexceeds a predetermined degree. by a pivoted actuating link 4 to theoperat- It is also an object of this invention to ing member 5 of thesnap movement mechaprovide a heat element included in the cirnism fortilting a'mercury tube switch 6 cuit adjustable to allow. apredetermined tov open and close an electric circuit there- 70 2amperage of the circuit to normally pass through. Figure 1 alsodiagrammatically therethrough and adapted to be so adjusted indicates anelectric circuit between the that an increase in the amperage to a resource of electricity, the switch 6, and the determined degree will meetwith sufiicient electric motor M. As indicated, a lead L resistance togenerate the amount of heat 'fI'OIIl the commercial source ofelectricityis 75 necessary to release the safety device. connectedto a binding post7 upon the rear While the preferred form of this inven of the casingwhich'binding post is connecttion is illustrated upon the accompanyinged by a flexible lead 8 to one terminal of the sheet of drawing, yet itis to be understood electric tube switch adjacent the end therethatminor detail changes may be made of. The other terminal of the switchad- 80 therein Without detracting from the scope jacent the. firstterminal is connected by a of the invention. flexible lead 9 to abinding post 10 on the 'In the drawings: back of the casin This bindingpost is Figure 1 is a view infront elevation of connected by leads 11and 12 throu h the an embodiment of this invention as applied safetydevice, to be hereinafter descri ed, to 5 to a pressure-actuated.mercury tube electhe binding post 13, which in turn is contricswitch,wit-h the cover removed. nected by a lead 14 tonne pole of the motorFigure 2 is atop plan view of Figure 1, M, the other pole beingconnected by thepartly in section. lead L tothe source of commercialcurrent.

I F gure 3 is a view in side elevation of The specific construction andoperation of 90 Figure 1, with parts broken away or the mercury tubeswitch mechanism is fully omitted, illustrating the construction of thedescribed in my prior application Serial No. safety device. 585,698,filed September 1, 1922, and as its Figure 4 is a fragmentary detailview construction forms no part of the present similar to. Figure 1,illustrating the posiinvention need only be described in general 95 tionin dotted lines assumed'by the parts terms. when the device has beenoperated by the A bracket 17 ofheat-transmitting matenormal expansion ofthe Bourdon tube. rial, such as brass, is supported bythree Figure 5 isa similar view illustrating the posts 18 froin a supporting platesecured 7 position assumed by the parts when the deupon the back ofthecasing 1, having a por- 100 vice has been operated bylan overload of hen19 perpendicular thereto and supportcurrent. a cup 20 in w hich isrotatively mounted a shaft 21 having a ratchet wheel 22 about the upperend thereof. The mercury tube tilting support 15 is provided with aplate 23 extending toward the back of the casing.

A safety actuating member in the form of a bell crank lever 24 ispivotally mounted upon the supporting plate at the rear of the casing torotate about a pivot adjacent its apex with the longer arm extendingover said extension 23 and the shorter depending arm. connected by acoil spring 25 to the rear of the casing which will normally exertsuflicient force upon the longer arm to rotate it about its pivot toengage the extension 23 and tilt the mercury tube switch into openposition, overcoming the switch mechanism normally holding the tube'inclqsed position. A member 16 of resilient metal is attached to the lever24 in prolongation of its shorter arm and adapted to act as a pawl atits free endand engage the teeth of the ratchet wheel 22.

The ratchet wheel 22 is normally held in fixed relation to the cup 20 bya film of solder so that when the pawl is in engagement with the ratchetwheel 22 the mercury tube switch will be held against rotation and whenthe solder is melted the ratchet wheel may be rotated to release thepawl and allow the mercury tube switch to be tilted to its openposition.

Within a cylindrical casing 26 of lavite or other electric insulationmounted between the supporting posts 18 and between the bracket 17 andback casing are arranged a plurality of super-imposed aphite disks 27. Astrip of mica. or other e ectric insulating material is interposedbetween the surface of the bracketl? and adjacent graphite disk and asimilar insulating medium is interposed between a movable member 28mounted at the oppositeend of the casing and the adjacent graphite disk.Said movable member 28 is adapted to impartpressure upon the series ofsuper-imposed graphite disks by the adjustable screw-threaded shaft 29passing through the rear of the casing. The lead 11 from the bindingpost 10 is placed in electrical connection with the graphite disk at oneend of the series and the lead 12 from the binding post 13 is lacedinelectric connection with the graph- 1te disk at the other end of theseries, so

I t that when the circuit is closed through the 6 the commercialcurfirst trough the merthe series of graphite mercury tube switch rentpasses in series, cury tube then through disks to the motor. Asillustrated, the normal position of the long arm of the bell crank lever24 when the pawl is in engagement with the ratchet allows-the support 15of the mercury tube switch-to be rotated about the pivot of theoperating mechanism by the expansion or contraction of the Bourdon tubeand when the pawl is released by the rotation of the ratchet wheel ifthe mercury tube switch is in the closed position'the lever 24 willcontact with the extension 23 and rotate the.

sure upon the series of graphite disks 27 may be so regulated by theshaft 29 passing through the rear of the casing that a com-- mercialcurrent of predetermined ampera e may pass therethrough to the mercurytufie switch' without enough to generate suflicient t to melt the solderin the cup 20 holding the ratchet wheel shaft 21 and upon increase ofthe amperage to a predetermined degree the resistance created by theseries of graphite disks will generate sufficient heat to melt thesolder and allow the spring pressed bell crank lever 24 to operate tothrow the switch into the open position and thereby break the commercialcircuit through the motor.

In order toreturn the parts to normal after having been operated by anoverload of current to release the safety device and the amperage andvoltage have decreased to or below the predetermined degree, a manualresetting device is provided, which comprises a pin 30 mounted upon thelever 24 adapted 24 and cause the pawl 16 to again engage the ratchetwheel 22.

In the form illustrated in Figures 1, 4

encounteringl resistance and 5, the parts are so arranged that the freeend of the longer arm of the bell crank lever 24 will, when released,engage the plate 23 to throw the switch tube into the open position.In-Figures 4 and 5 the under side of thislonger arm is cut away betweenits free end and pivoted apex to provide a depending nose 33 and heel 34and the plate Ill) 23 is secured to the mercury tube support 15 in sucha manner that. when an overload of current releases the lever 24, thenose 33 thereof will engage the plate 23which will pass free of the heel34.in throwing the switch tube into the open position.

In Figures 6 and 7 the mercury tube switch is caused to close thecircuit therethrough upon the normal Bourbon tube'by reversing theposition of the mercury tube, that is, by inserting the tube in thesupportin clips with'the terminals at the right 0? the casing. In thiscase the plate 23 is secured to the mercury expansion of the tubesupport 15 in such amanner that when to prevent an overload therethroughcoman overload of current releases the lever prising in combination witha mechanically- ,T 24. the heel 34 thereof will engage the plateoperated electric switch, an additional me- 23,which will pass free ofthe nose 33 in chanical actuator therefor adapted to open throwing theswitch tube into the open pothe switch to open the circuit therethrough70 sition. detachably held in inoperative position by a While thisembodiment has illustrated and thermal connection, electric meansincluddescribed the series of superimposed disks ing a plurality ofsuper-imposed-discs of forming the heat generating unit ofvaryconductive material, the conductivity of.

ing conductivity. in inverse proportion to which varies in accordancewith the pressure 75 pressure placed upon the disks as being appliedthereto, and the pressure so adjustformed of graphite, it is to beunderstood ed as to be actuated by an increase in ourthat othermaterials such as carbon or comrent passing therethrough whereby there-. positions of material that will act as elecsistance offeredenerates suflicient heat to tric'al conductors, may be used in place ofrelease said hold ing means and allow the so the graphite disks toproduce the same reswitch to be operated to break the circuit sult.therethrou h.

' What I claim is: n 5. A sa ety device for an electric circuit 1. Asafety device for an electric circult to prevent an overloadtherethrough, comto prevent an overload therethrough com-- prising incombination with a mechanically- 85 prising in combination with amechanically-' operated electric switch havin a tlltlllo' operatedectric wi h, a a l l movement about a pivot, an additional mechanlcal acua or h r for ad p ed to op chanical actuator therefor comprising apivthe switch to open the circuit therethroug oted actuating levernormally adapted to endetachably held in ino erative posit on y gage androtate said switch to open the cir- 00 a thermal connection, e ectricmeans in an it th th h, id t ti lever d cu 1t with saidswitch andS0l1rCe f 1 tachably held in inoperative position by a melt? .90 P g aplurality 0f P thermal connection, electric means in circuit pose dlSCSadapted to actuated by an nwith said switch and source of electricity 3ocrease in current passing therethrough comprising a plurality ofsuperimposed discs C1'f5a$ing f temperature thereof to Pele/55b adaptedto be actuated by an increase in Sald' holdmg means allow F W1tcb totemperature passing therethrough increasing be Operated to b the cllculttherethe temperature thereof to release said holdig o ing means andallow the switch to be oper- 5 2. safety device for an electric circuitated to b a h i it th th h mu b n fibel'etbrougb A safety device for anelectric circuit Prlslng 1n comblnatlbn W bb to prevent an overloadtherethrough com; p b electnc swltch, an addl'twnal m prising incombination with a mechanicallychanlcill actuator therefqr f p to poperated pivoted. electric switch, an addi- 4 the swltch to P btbebefihl'ough tional mechanical actuator therefor comprisdetachablyhe1d 1n lnopeliltlve P y ing a pivoted actuating lever normally thermalconnectlon, electric means 1n circuit d t d t engage d t t th l t iwilfh Said Switch and S F of b fil'f i y switch about its ivot to openthe circuit adlustable to predetermlned condubblvlty therethrough, saiclactuating lever detachp d be actuated y all-Increase 111 ably held ininoperative position by a ther- U0 rent p g t q g generate heat malconnection, electric means including a Suficlent to release sald meansand of superimposed discs of ,conduc allow the switch to be operated tobreak the ti t i l th d ti it f hi h cll'culb therethrough .varies withthe pressure applied thereto, and

50 A safety devlce for an elecbllc cllbult the pressure so adjusted asto be actuated 115 tO BI'GVtEHt an {overload therethrough C0man increasein Current passing there- Pr1S1I1g1I1-c0mbmfit19n Wlth bb ythrough,whereby the resistance offered ge Operated electllc Swltch, alladdltlonal erates suflicient heat torelease said holdin b b abtuator q dp to p means and allow the switch to be operated to 55 the switch toopenthe circuit therethrough b k th i it th thr ugh,

detachably dinm pe PQ y a 7. A safety device for an electric circuitthermal connection, electric means including t v t an overloadtherethrough coma plurality of super-imposed discs of varyprising incombination with a mechanicallying conductivity so adjusted as to beacoperated pivoted electric switch, an addi 6o ,tuated by an incr in r npassing tional mechanical actuator therefor compristherethrough wherebythe resistance ofi'ered 'ing a pivoted actuating lever normallygenerates suificient heat to release said holdadapted to engage androtate the electric mg means and allow the switch to be oper switchabout its pivot to open the circuit ated to break the circuittherethrough. therethrough, said actuating lever detachc5 4;. A safetydevice for an electric circuit ably held in inoperative posi n by athen-1 30 mal connection, electric means includin a plurality ofsuperimposed discs of con uc- 'tiv'e material, the conductivity of whichvaries with the pressure applied thereto, and 5 the pressure s0 adjustedas to be actuatedby an increase in current passing therethrough, wherebythe resistance ofiered generates sufficient heat to release said holdingmeans and allow the s 'tch to be operated to break adjustment forfadjustlng the conductivity of the discs and an exterior manual resetfor rotating the switch to the closed position.

4 IRA E. MQCABE;

the circuit therethrough, an exterior hand 10

